Silicon based devices that exhibit a negative differential resistance (NDR) characteristic have long been sought after in the history of semiconductor devices. A new type of CMOS compatible, NDR capable FET is disclosed in the following King et al. applications:
Ser. No. 09/603,101 entitled “A CMOS-PROCESS COMPATIBLE, TUNABLE NDR (NEGATIVE DIFFERENTIAL RESISTANCE) DEVICE AND METHOD OF OPERATING SAME”; and
Ser. No. 09/603,102 entitled “CHARGE TRAPPING DEVICE AND METHOD FOR IMPLEMENTING A TRANSISTOR HAVING A NEGATIVE DIFFERENTIAL RESISTANCE MODE” now issued as U.S. Pat. No. 6,479,862 on Nov. 12, 2002; and
Ser. No. 09/602,658 entitled “CMOS COMPATIBLE PROCESS FOR MAKING A TUNABLE NEGATIVE DIFFERENTIAL RESISTANCE (NDR) DEVICE;
all of which were filed Jun. 22, 2000 and which are hereby incorporated by reference as if fully set forth herein. The advantages of such device are well set out in such materials, and are not repeated here.
As also explained in such references, NDR devices can be used in a number of circuit applications, including multiple-valued logic circuits, static memory (SRAM) cells, latches, and oscillators to name a few. The aforementioned King et al applications describe a break-through advancement that allows NDR devices to be implemented in silicon-based IC technology, using conventional planar processing techniques as for complementary metal-oxide-semiconductor (CMOS) FET devices. The integration of NDR devices with CMOS devices provides a number of benefits for high-density logic and memory circuits.
It is clear, from the advantages presented by the above-described NDR device, that overall improvements in manufacturing, testing and operation of the same are desirable to refine and proliferate such technologies.
In addition, enhancements in trap location control, trap energy level control, and trap formation, are also useful for these types of NDR devices, and could be beneficial to other types of trap-based devices as well.
Furthermore, the prior art to date has been limited generally to devices in which the peak-to-valley ratio (PVR) is not easily adjustable. It would be useful, for example, to be able to control the PVR directly during manufacture, so as to permit a wide variety of NDR behaviors for different circuits on a single die/wafer. Alternatively, the ability to control PVR during normal operation of a device would also be useful, but is generally not possible with current NDR technologies.